1. Field of the Invention
The present invention relates to a tire vulcanizing method for vulcanizing and molding a green tire, and a tire vulcanizer.
2. Description of the Related Art
In order that a green tire is vulcanized and molded by a bladder type tire vulcanizing press, the tire is subjected to shaping by a bladder, the tire is mounted within a mold (metal mold), and a heating medium (heating gas, steam or the like) is supplied into the bladder, and in case of a bladderless tire vulcanizing press, upper and lower bead portions of a green tire are held, the tire is mounted within a mold, and a heating medium is supplied into the tire whereby vulcanizing and molding are applied by denaturation of rubber caused by heating.
However, the green tire is uneven in thickness as shown in section of FIG. 45, and in order to prevent an unvulcanized tire from occurrence in a vulcanizing press, the vulcanizing time is set with a rise of temperature of a tread portion R and a bead portion V in the thick portion. Therefore, even if the inside and the outside of a side wall portion S in the thin portion of the green tire reach a vulcanizing temperature, there has to wait for till the inside of the tread portion R and the bead portion V in the thick portion reaches a vulcanizing temperature, not only causing the rise in production cost resulting from the loss of the heat energy, but also prolonging the cycle time of the tire vulcanization, thus causing the productivity to lower.
Particularly, in the case of vulcanizing and molding using a bladder, this bladder is heated by the heating medium to heat the inner circumference of the green tire, because of which the heat conductivity is poor, and it takes long time till a temperature is risen up to vulcanizing temperature.
The inner circumference of the green tire is strengthened by an inner liner portion L as shown in FIG. 45. This inner liner portion L is normally pasted to the inner circumference of the green tire so that the ends thereof are superposed to each other, and in the vulcanizing and molding by the bladderless tire vulcanizing press, functions as a substitute of a bladder for putting a shape of a green tire in order. Accordingly, when the heating medium directly applies to the inner liner portion L by the bladderless type tire vulcanizing press, the heating medium enters from the joints or scratches to possibly turn up the inner liner portion L, and since the heating pressure medium exerting on the inner liner portion L is static pressure, the vulcanizing and molding are to be done in a state of leaving the joints or scratches, greatly influencing on the quality and external appearance of the tire vulcanization.
It is an object of the present invention to shorten the cycle time of tire vulcanization to improve the productivity.
A first invention is to vulcanize and mold a green tire using a bladder and a tire vulcanizing press, and provides a vulcanizing method comprising: applying shaping to a green tire externally of a tire vulcanizing press, and then applying vulcanizing and molding to the whole tire subjected to shaping by the tire vulcanizing press.
In this case, the bladder is elevated in temperature in advance by heating gas, prior to vulcanizing and molding by the press, to apply shaping to the green tire, and therefore, the time for restricting the tire by the press is shortened.
Further, the vulcanizing and molding of the whole green tire is not carried out by the press, but the shaping of the green tire, the heating of the bladder, and the vulcanizing and molding of the tire subjected to shaping are separately carried out whereby the vulcanizing can be carried out in parallel, whereby the cycle time of the tire vulcanization can be shortened totally.
Further, in the pre-processing step, when pre-heating is applied to the green tire, the restricting time of the tire in the tire vulcanizing press can be further shortened. Particularly, when the pre-heating is applied to the thick portion of a tread portion and a bead portion of a green tire, and the thick portion is heated to a temperature immediately before starting of vulcanization, the procedure can be shifted immediately to the vulcanizing and molding by the press.
Further, when in the pre-heating step, a bladder delivered out of the press is used, the time for heating the bladder by the pre-heating means can be shortened because the bladder is heated by the press.
A second invention is to apply vulcanizing and molding to a green tire using a bladder type tire vulcanizing press, and provides a vulcanizing method comprising: applying pre-heating to a green tire externally of the press, and then applying vulcanizing and molding to the whole tire preheated by the press.
In this case, since the tire preheated by the press is subjected to vulcanizing and molding, the time for restricting the tire by the press is shortened.
Further, the vulcanizing and molding of the whole green tire is not carried out by the press, but the preheating of the green tire, and the vulcanizing and molding of the preheated tire are separately carried out whereby the vulcanizing can be carried out in parallel, whereby the cycle time of the tire vulcanization can be shortened totally.
Further, in the pre-step, when pre-heating is applied to the thick portion of the tread portion and the bead portion of the green tire, the time for heating the thick portion to the vulcanizing temperature by the press can be shortened. Particularly, when heating takes place to the temperature immediately before starting of vulcanization, the procedure can be shifted immediately to the vulcanizing and molding by the press.
Further, a third invention is to vulcanize and mold a green tire using a bladderless type tire vulcanizing press, and provides a tire vulcanizing method comprising: applying pre-vulcanization to a green tire externally of the press, and then applying vulcanizing and molding to the whole tire preheated by the press, and a tire vulcanizer.
Since the preheated tire is subjected to vulcanizing and molding by the tire vulcanizing press, the time for restricting the tire by the press can be shortened. Further, when the pre-vulcanizing is applied to the green tire simultaneously with the preheating, the time for restricting the tire by the press can be further shortened, and even if only the pre-vulcanizing is applied, the time for restricting the tire by the press can be shortened.
Further, the vulcanizing and molding of the whole green tire is not carried out by the press, but the preheating or the like of the green tire, and the vulcanizing and molding of the preheated tire are separately carried out whereby the vulcanizing can be carried out in parallel, whereby the cycle time of the tire vulcanization can be shortened totally.
Further, in the pre-step, when pre-vulcanizing is applied to the inner liner portion of the inner circumference of the green tire, uneven portions such as joints or defects of the inner liner portion can be smoothed (uniformed) and repaired. When low pressure heating gas exerts on the inner liner portion while rising temperature, vulcanization does not reach the inner layer of the tire but rubber can be caused to have the flowability merely by the surface of the inner liner portion to apply the pre-vulcanization to only the inner liner portion positively.
In the pre-step, when pre-heating is applied to the thick portion of the tread portion and the bead portion of the green tire, the time for heating the thick portion to the vulcanizing temperature by the tire vulcanizing press can be shortened. Particularly, when heated to the temperature immediately before starting of vulcanization, the procedure can be shifted to the vulcanizing and molding immediately by the press.
When the pre-processing means is caused to have a function for delivering a green tire and a pre-vulcanized tire, in addition to pre-vulcanization and pre-heating, the tire vulcanizer can be miniaturized.